"Fifty-one percent of Americans identified as Protestant or other non-Catholic Christian in 2013, making this by far the largest major religious grouping in the country. All 10 of the most Protestant states are located in the South," according to Gallup's Frank Newport, who authored the firm's article about the survey results.

Gallup also noted the unique role of The Church of Jesus Christ of Latter-day Saints in Utah, saying, "The least Protestant state is heavily Mormon Utah, which is only 11% Protestant."